In earlier devices of this type, the clamp segment raises the upper inlet roller from the lower inlet roller and secures the roving or sliver against the upper inlet roller. The clamp segment is acted upon by an actuating element which brings it into its roving or sliver-clamping position. The clamp segment is maintained by a holding element in the position in which the roving or sliver clamping device is in its inoperative position or at rest, i.e. the roving or sliver releasing position.
A roving or sliver clamping device of this kind is known in which the clamp segment is provided with a coupling-type projection which, in turn, engages the counter-piece of a support rail which is spring-biased (German Pat. No. 34 06 397).
The support rail, in turn, is connected to a solenoid which serves to release the latch so that, due to the force of the spring and with the correlated rotation of the lower inlet roller, the clamping segment enters between the roving or sliver and the lower inlet roller and raises the upper inlet roller out of the contact with the lower inlet roller while clamping the roving or sliver against the upper inlet roller.
Another roving or sliver clamping device of this general kind includes a contact formation which locks a lever. On release the lock the clamp segment is taken along in the direction of rotation by the lower inlet roller, and the supply of roving or sliver is stopped (German Pat. No. 30 48 481).
Due to their particular structures, the prior art devices briefly described in the foregoing do not always ensure a fully satisfactory action which will ensure that the respective components are positively moved from the released position into the clamped position or condition, i.e. assume the position in which the upper inlet roller is lifted from the lower inlet roller and in which the roving or sliver or roving is pressed against the upper inlet roller.
Practical experience has shown that the respective catch elements which absorb the operational pressure or impact sometimes jam due to the exerted pressure and do not positively or assuredly disengage when this is necessary.